A new study from the University of Toronto finds that people perceive their bodies as larger in virtual reality than in the physical world - and that effect doesn't end when the headset comes off.
Researchers at U of T's Faculty of Kinesiology & Physical Education (KPE) set out to test how accurately people judge their own body size relative to their surroundings in VR.
Participants embodied a life-sized avatar to explore a virtual world built to match the scale of the real one, and were then asked to estimate the minimal distance needed to clear a gap between two poles.
The study, recently published in the Virtual Reality journal , found that participants predicted they would need a wider gap in VR than they did outside it.
Xiaoye Michael Wang, a research associate at KPE who co-authored the study with Professors Tim Welsh and Catherine Sabiston, compared the effect to Gulliver's Travels, in which the story's protagonist wakes to find himself a giant among tiny people.
"It was surprising to find how much larger people seemed to perceive their body in VR," Wang says. "People behaved as though their body had become larger relative to the world around them, even though nothing had actually changed in scale."
Notably, this effect was not limited to the time participants spent inside VR. The researchers found that after taking their headsets off, participants still judged that they needed slightly wider openings in the physical world than they had before entering VR.
"The effect carried over after participants returned to the real world, suggesting that VR had temporarily recalibrated how they perceived the relationship between their body and surrounding space," says Wang.
The researchers identified two main explanations. First, because movement in VR was less precise, participants may have given themselves more room than necessary to pass through the opening without bumping into anything. Second, VR also changed visual perception itself: the opening appeared narrower than it was intended to be, which made people think they needed even more space.
"Our modelling suggested that a major source of this distortion was depth compression created by the VR headset, known as the vergence-accommodation conflict," says Welsh, associate dean of research at KPE, specializing in cognitive and neural motor behaviour.
"In simple terms, the visual system receives mismatched depth signals when wearing a VR headset, which can make space seem compressed - smaller than it actually is or is intended to be - and cause an opening to look narrower than it really is."
These findings matter because VR is increasingly being used for training, education, rehabilitation and other settings where people need to judge space accurately and move safely. But VR isn't always a reliable proving ground.
Researchers found that performance in VR partly reflects how well someone has adapted to the system's distortions - adjustments that can work against them when putting those skills into practice.
"If people learn in VR to leave more room than they actually need, or if they misjudge the space available around them, then the strategies they develop in VR may not translate cleanly to real-world performance," says Wang.
At the same time, the researchers say these findings are encouraging because they also point to a solution.
Once the researchers mathematically corrected for VR-specific distortions, people's judgments in VR lined up much more closely with what their bodies could actually do at a real-world scale.
"This finding suggests that people are still perceiving the world in a functionally meaningful way in VR, but they are doing so under altered viewing conditions," says Wang.
"That result gives us a clearer target for improving VR systems: if we can reduce or compensate for these distortions, VR-based training may become more accurate, more effective and more transferable to the physical world."
For Sabiston, the research also raises possibilities for how VR's ability to shift self-perception could be harnessed to help people struggling with body image.
"For individuals who experience body-related stigma, internalized weight bias or negative body-related emotions, physical activity settings can sometimes feel uncomfortable or discouraging," says Sabiston, who is Canada Research Chair in physical activity and psychosocial well-being.
"We are interested in whether VR could provide a new way to support these individuals by allowing them to interact through a virtual body and, in turn, potentially shift how they perceive and relate to their own physical body."
This research received support from the New Frontiers in Research Fund and the Natural Sciences and Engineering Research Council of Canada.
